1) Because once you use an EREV, you'll be reluctant to use gas and will only want to run on electricity. Therefore, you'll develop charging anxiety, constantly checking your battery level and looking for a place to charge.
2) EREVs require additional maintenance for the internal combustion engine, which is a waste of time and money.
3) EREVs have a bad reputation. Your family and friends will ask you why you didn't buy a pure EV instead of this outdated technology, which will cause you quite a bit of frustration!
4) After buying an EREV, you'll constantly think about switching to a pure EV. Conclusion: Don't buy an EREV unless you can accept these drawbacks! Of course, EREVs do have many advantages as well!